A Level Biology Revision Notes

Comprehensive A Level Biology revision notes providing information and assistance for all UK examination boards (AQA, OCR, Edexcel) as well as international curriculum (CIE).

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Adaptations to photosynthesis

Introduction Photosynthesis means the production of food using light energy. This process takes place in plants and some other organisms such as Algae and cyanobacteria. These organisms are called phototrophs. They utilize water and carbon dioxide and make sugars and starches. Oxygen is released as a byproduct, and then other organisms such as humans use …

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Antibiotics

Introduction Different drugs have been developed over the past centuries to combat various disease processes that occur in living organisms. Several of these drugs prove lifesaving in many instances. Antibiotics are drugs that work against bacteria. They either kill bacteria or stop their growth within the bodies of other living organisms. They are used worldwide …

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Antibodies and Vaccination

Introduction Antibodies are plasma proteins that are found in the blood of vertebrates. They are a component of the immune system that protects the bodies of living organisms against harmful disease-causing agents. Different foreign organisms enter our bodies while we are performing daily life activities. Antibodies and other components of the immune system protect our …

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Infectious Diseases

Introduction The entry of any living organism into the body of a person is called infection. Diseases that are caused by the entry of the living organism into the body of a person are called infectious diseases. These are the diseases caused by living organisms like bacteria, fungi, viruses, or parasites. The organisms responsible for …

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Stem cells: A General Overview

Introduction Considering an adult human body, scientists have proposed that it is composed of about 200 different cell types, each with its specific function. Among this diversity, the most important ones are the Stem cells. A general concept about them is that these are the parent cells that give rise to all other cell types. …

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Chromosome Behaviour During Mitosis

Introduction Chromosomal behaviour is just the normal movement of chromosomes during cell division. During mitosis, replicated chromosomes align themselves along the equator of the cell forming a metaphase plate, and then sister chromatids are pulled apart towards opposite poles of the cell. All these complex activities are highly coordinated and controlled by various signals and …

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Enzyme Catalysed Reactions

Introduction Enzymes are the natural catalysts present in the bodies of living organisms. They are the globular proteins made to function inside as well as outside the cell. They catalyse thousands of chemical reactions taking place within the living bodies. Enzymes are needed for the metabolic reactions. If there are no enzymes, metabolism will stop, …

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Enzymes: Mechanism of Action

Introduction Enzymes are the protein substances that are needed for all the biochemical reactions taking place in the living cells. They catalyse chemical reactions that are essential for life. They are involved in processes like digestion and breakdown of nutrients, metabolism of nutrients to provide energy, synthesis of proteins, DNA, and other biomolecules, etc. They …

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Globular Proteins

Introduction Proteins are the most abundant molecules found in living organisms. They play structural as well as functional roles in the bodies of living organisms. As structural molecules, they are present in nuclear material, cell membrane, cytoskeleton, etc. They are present in every organelle and every cell of a living organism. Almost all the functions …

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Intracellular and Extracellular Enzymes

Introduction Enzymes are the protein substances that speed up the chemical reactions taking place in the bodies of living organisms. The presence of enzymes is essential for life to continue. Without enzymes, metabolism will stop, and life will stop to exist. Enzymes can catalyse chemical reactions both in the cytoplasm or organelles within the cell …

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